Developing a 15-minute city: A comparative study of four Italian Cities-Cagliari, Perugia, Pisa, and Trieste

The pandemic and the environmental crisis raise the question of a radical transformation of cities to foster inclusion, sustainability, participation, and quality of life. The 15-minute city concept prefigures a reorganization of urban spaces, structures, and functions aimed at increasing residents’ access to essential services, favoring sustainable modes of transportation, and transforming public urban spaces into multifunctional places. The proposed study develops a set of indicators derived from the spatial and configurational analysis to evaluate the compliance of urban systems with the 15-minute city concept. The selected areas of study are the cities of Cagliari, Perugia, Pisa, and Trieste, in Italy. The study investigates four issues: i) defining a set of relevant, reproducible, and comparable indicators for measuring density, proximity, and diversity; ii) investigating the influence of distinct urban planning concepts, manifested by distinct spatial configurations, on density, proximity, and diversity; iii) defining urban scale metrics to measure levels of spatial injustice in terms of unequal conditions of access to essential services and iv) measuring the correlation between configurational factors and access to services. The analysis underlines the gap in access to essential services among central compact districts and dispersed outer areas, thus enabling the identification of inequalities in the distribution of spatial capital. Moreover, the study underlines the relationship between the urban environment structure and the location of functions. As a result, the study emphasizes that the proposed set of indicators is instrumental to understanding the urban environment's potential to meet urban populations' needs and facilitating informed decisions in urban planning.